AbstractPrepreg-based composite parts require good mechanical properties of both fibre reinforcement and polymer matrix, as well as good processability when forming them into desired shapes without quality issues. Among various mechanical properties of interest, delamination resistance has been one of the major requirements for aerospace composite components. Interleaving thermoplastic microparticles particles is a cost-effective interlaminar toughening method. However, most previous studies have mainly focused on their toughening effect and mechanisms, their impact on the processability of composites has not been well investigated yet.
In this work, a method of directly depositing dry polyamide particles on prepreg materials was used as an alternative to conventional interlaminar toughening methods. The aim of this work was to investigate the effect of particle’s physical parameters on both the toughening effect and the material processability and formability.
This thesis includes three parts. The first part presents the fracture toughness of laminated composites interleaved with a range of toughening materials. The effect processing conditions and particle characteristics on interlaminar fracture toughness were discussed. The second part investigates the processability of the particle-toughened laminates in diaphragm forming and autoclave curing, which includes an in-depth investigation on the interply friction and the compaction behaviour of uncured prepreg stacks with interleaving particle tougheners. Finally, L-shaped composite beams interleaved with different tougheners were manufactured to validate the effect of the toughening materials on the forming and curing qualities. The correlation between forming/curing and material characterisation results was discussed.
This work demonstrated that the direct particle deposition method is a very effective toughening method which could improve both the interlaminar fracture toughness and the processability of prepregs. It was also found that careful selection of a suitable particle type considering its impact on material processability would be important, otherwise the toughening effect might counteract the manufacturing quality.
|Date of Award||28 Nov 2019|
|Supervisor||Byung Chul (Eric) Kim (Supervisor)|